Method of and means for amplifying potential variations



Sept. 18 1923. 1,468,116

I. LANGMUlR METHOD OF AND MEANS FOR AMPLIFYING POTENTIAL VARIATIONSFiled Dec. 10. 1914 EQa-ANXN 0 ll 40 60 80 I00 A80 /40 I60 I80 200 220240 Witnesses: Inventor His JTttorneg Patented Sept. 18, 1923.

UNITED STATES PATENT OFFICE.

IRVING LANGHUIB, 01' SCHENEGIADY, m YORK, ASSIGNOB '10 GENERAL ELECTRICCOIPANY, A OOBPORATION 01 NEW YORK.

mnon 0! AND MEANS FOR AHPLIFYING POTENTIAL VARIATIONS.

Application filed December X0, 1914. Ierlal llb.-876,432.

To all whom it may concern:

Be it known that I, Iavmo Lanomna, a citizen of the United States,residin at Schenectady, count of Schenectady, tate of New York, haveinvented certain new and useful Improvements in Methods of and Means forAmplifying Potential Variations, of which the following is aspecification.

present invention relates to the amplification of potential variationsand more especially to the utilization in a wireless receiving system ofdevices having certain peculiar current limitin characteristics.

One of the objects 0 my invention is to provide a simple and etlicientmeans for amplifying the potential variations of received waves ofradiant energy. A further object of my invention is to provide a systemin which all of the electrical impulses received by an antenna may beamplified and the wave shape of the original impulses may be maintainedsubstantially the same u to a desired oint in the amplification. tillanother ob ect of my invention is to provide a system in which theeffects upon the receiving apparatus of the atmospheric condition knownas static may be greatly reduced.

It has been discovered that if two elecprovide a simple and etiicientmeans for for causing it to emit electrons, are enclosed in an envelopeexhausted to such a degree that the passage of current between theelectrodes produces substantially no gas ionization, irrespective of thevoltage employed, the How of current is dependent upon certainconditions. In case a heated cathode is used the current with constanttemperature of the cathode, will, between certain limits, vary as the3/2 power of the voltage impressed on the anode. As the voltage isincreased, however, a point which may be termed the saturation point, isfinally reached at which the current becomes constant. By varying thetemperature of the cathode the impressed voltage at which the currentbecomes constant may be varied and the value of the saturation currentmay be varied. Devices of this type are described and certain broadfeatures thereof are claimed in my copending application, Serial No.84,242, filed March 14, 1916, which is a continuation of my applicationSerial No. 7 95.610, filed October 16, 1913.

If a negative electrostatic field is set up within the envelo of anelectron discharge device in which t e current has not reached thesaturation point, by impressing a negative (potential upon a conductinggrid interpose between the electrodes the flow of current will bedecreased, and if the negative potential used is great enough withrespect to the potential impressed on the anode the flow of current maybe sto ped altogether. ()n the other hand if a positive potential isimpressed upon the grid the flow of current may be increased. Incontrolling the current in this way if the anode is maintained at aconstant potential a small variation in the potential of the grid willcause a very large change in the current between the electrodes. Thisproperty of such devices has been made use 0 by impressing u on the gridthe otential of the very fee le current impulses of Waves of radiantenergy such as are received by the antenna of a wireless station.thereby producing a current flow between the electrodes which varies inaccordance with the variations in the received current, but which is ofmuch greater amplitude. If on the other hand, it is desired to cause aconstant current to flow through the device the anode potential requiredto produce that current will vary in accordance with the variations inthe potential of the grid. In carr ing my invention into effect I makeuse of t is last property in such a way as to amplify the potentialvariations of the received waves instead of the current varia tions andby so doing secure a high degree of amplification. In accomplishing thisresult I may also make use of the current saturation effect of a secondelectron discharge device to prevent the current through the amplifierfrom exceeding a certain amount, irrespective of the voltage impressedupon the mid.

b In the operation of a receiving system arranged in accordance with myinvention all of the potential variations of the received waves ofradiant energy on a strongly damped antenna may be amplified in theirproper roportions. The amplified potential variations thus obtained maybe impressed upon a current limiting device which will eliminate all ofthe current impulses above a redetermined value and in this way the eect of heavy static discharges may be avoided. After the large impulseshave thus been removed suitable tuning apparatus may be employed toselect the impulses from other stations also serves. as a path to themind for atmospheric electricity common y known as static. This may becollected by the antenna merely by contact with charged atmosphere. Thegreatest interference with the receiving of the desired waves is,however, due to electromagnetic waves produced by atmospheric dischargesaccompanying thunder storms at a distance. When receiving from a stationsending out strong signals and not too far away,- the ener of thesewaves produced by atmosheric discharges which reach the antenna isusually sosmall in comparison with that of the signaling waves thatthere is prac tically no interference with the signals which it isdesired to receive. On the other hand when an attempt is made to receivesignals which are so weak when they reach the antenna that amplificationis necessary for receiving, the amplitude of'these waves produced bystatic discharges may become much greater than that of the signals whichare to be received. If the antenna is tuned to the frequency of thewaves to be received oscillations of the same frequency but of muchgreater amplitude than the received waves will be set up therein by thewaves produced by static discharges. The duration of these oscillationsis comfiarativel short but if, in order to receive t e signa desired,amplification is necessa the waves produced by static will be amp ifiedto the same extent as the'other waves. As a result the amplified staticoscillations will produce such a loud noise in the telephone ordinarlyused as a receiver as to completely drown out the desired signals over arnuc greater period. If the antenna is strongly damped no oscillationswill be set u therein but the energy of the wave p need by static willass to earth as a single rush of current. ith such an antenna thereceived signals are weaker than when the antenna is tuned, while theamplitude of the static impulse remains substantially the same. As aresult the am litude of the signaling waves becomes much ess withrespect to the static impulses than when a tuned antenna is used forreceiving. a If then a device is placed in the receiving system, eitherbefore or after amplification, which limits the current which can reachthe receiver'to a value approximately that of the waves to be received Areceiving antenna in addimeans the efl'ect of the static charge on thereceiver ma be so reduced as to be practically negligi le.

The novel features of my invention are pointed out with particularity inthe ap-. pended claims. The invention itself, however, together withfurther objects and advantages will best be understood by referencetothe following description taken in connection with the accomanyingdrawing in which Fig. 1 illustrates iagrammatically a receivingsystem; Fig. 2 illustrates the application of a current limiting deviceto reduce the effect of static disturbances; Fig. 3 shows a curveillustrating the current saturation efi'ect of an electron dischargedevice, and Fig. 4 shows the relation between the anode potential andgrid otential of an electron discharge device wit a constant current.

As indicated in Fig. 1 the antenna 1 is inductively connected by meansof the transforming device 2 to the grid 3 of an electron dischargedevice 4. This device comprises in addition to the grid 3 an anode 5which preferably is plate shaped, and a cathode 6 of filamentary formwhich is provided with a battery 7 for heating to incandescence. Forconvenience of description I term the circuit which comprises the grid3, the secondary of the transformer 2, and the cathode 6, the idcircuit. The envelope within which t ese electrodes are placed ispreferably exhausted to such a high degree of vacuum that the passage ofcurrent between the electrodes is accompanied by substantially no gasionization irrespective of the voltage employed. In series with theelectrodes of this device a source of energy 8 is placed and a secondelectron discharge device 9 is also included in the circuit which forconvenience of description I desi ate as the plate circuit. This seconddevice is similar to the first with the exception that the grid may beomitted. This device, however, should be so designed that with theordinary temperature at which the cathode 10 is best adapted to operatethe current will reach its maximum value when the voltage impressed uponthe anode 11 is considerably less than that of the source of energy 8.The two devices should be so related and the potential of the sourceSshould be adjusted that normally the saturation current of the. device 9will be less than that which would pass through the device 4 when thegrid 3 15 at the normal potential. If then the grid potential be variedthe current through the device 4 will tend to vary. Inasmuch, however,-as this current is kept constant by the current limitin device 9 novariationin the current throng the device 4 is possible. As

the grid potential is varied, however, the difference in potentialbetween the cathode 6 and the anode 5 will vary and consequently thepotential difference between the cathode 10 and the anode 11 of thecurrent limiting device 9 will vary. The variations thus produced,however, will be many times ter than the variatiom of the potential ofthe grid 3. These amplified potential variations may be imp upon thegrid of a third electron discharge device 12 similar to the first one.Since the variation in potential between; the cathode 6 and the anode 5is equal to'that between the cathode 10 and the anode 11 of the currentlimiting device 9 the potential variations between cathode 6 and anode 5may be impressed on the fill of the device 12 with the same result. Ithe connection is made in this war it will be possible to use a somewhatvariable source of enerw in place of battery 8 since variations in thepotential of the source will have no effect on the potential betweencathode 6 and anode 5 as lon as the potential of the source 8 is greaterthan that required to produce saturation current.

In this case the variations in potential of the source 8 will be alltaken up by the device 9. While the variations in potential hctwcen 6and 5 will ditl'er from those between 10 and 11 by an amount equal tothe variations of the source 8 this will not affect the operation of thedevice as the potential variations between 6 and 5 will always beproportional to the changes in potential of grid The late circuit of thedevice 12 ma in addition to the source of energy 13 inc ude n secondcurrent limiting device. and the potential variations impres ed upon thegrid 14 may be again amplified as in thc first case. As many of thesedevices may be connected in series as is necessary to secure the desireddegree of amplification. When the potential variations have beenamplified as much as desired thev may be used to control the currentthrough the lust electron discharge device of the series. therebyproducing in the plate circuit of that dcvice a current whici varies inaccordance with and is many times greater than the current received inthe antenna.

If the antenna 1 is strongly damped all of thc waves of radiant energyreceived thercby will be amplified to the same degreeand i none of thecircuits connecting the amplifiers are resonant the wave shapes of thevarious impulses received will be amplified with little variation. Bypassing the amplified current thus obtained through a tit) tuned circuitconsisting of an iluluclancc If and variable condenser 16. it will bepossible to sclcct thc ampllfied waves of the frequency which it isdesired to rcccivc. The

waves thus selected may then be impressed upon the grid circuit ofanother electron discharge device 17 and the received signals may bedetected in the telephone receiver 18 conncctcd to the plate circuit ofthe detector 17.

thc resistance 22.

In the drawin I have shown only one potential ampli yin device, but haveindicated by dotted lines the point in the system at which additionalpotcntial amplifyin devices may he connccted.

n the system .thus far described no provision has been made foreliminating the heavy static im ulses which are received on the'antenna.a n arrangcmcnt for accomplishing this is indicated in Fig. 2 in whichcurrent from a device controlled by am ililied potcntial variations iscaused to ow through the coil [9. The current thus obtnincd may comprisercccivcd waves from a plurality of stations and in addition may containimpulses from Qatic charges of much greater amplitude than the signalingwaves. To eliminate all of these impulses of an amplitude greater thanthat of the signaling waves, a current limilin r device 20 having twoincandescent clcctroi es. in order to allow the pnssugc of currcnt ineither direction. may be included in the circuit of the coil 21 which iscoupled with (oil 19. The signaling waves will pass throu h this currentlimitIng device without ditlicnlty'. .-\s soon as a wave of highamplitude doc to a static impulse is induccd in the circuit the currentlimiting action of the dcvicc takes ctl'ect and only a small portion ofthe wave is allowed to pass through. The energy of the wave which docsnot pass througi the current limiting device may be absorbml in Havinthus eliminated the heavy static impulses the current may be reproducedin thc tuned "rid circuit of the detector 23 in order to select anddctcct the waves of a desired l'riulucncy. \l'hilc lhu vo indicated thecurrent limiting device us being connected in the system al'tcr thcdesired potential amplification has been obtained it will be apparentthat it may be located at an point. in the system where thc current vano of thercceived wuvcs docs not differ greatly from the saturationcurrent of the device. in the operation of electron discharge deviceshavin a controlling grid it will be found desirable to, adjust thenormal potential of the grid to a value at which the device has thegreatest scnsitivcncss to variations in the grid potential. in order todo this a battery 24 of the desired potential may be connected to thegrid. in some cuscs the positive lcrmiuul may be connectcd to thc gridwhile in other cases it will he found desirable to connect thc negativeterminal of this battery to the grid.

The curve of Fig. 3 which is'drawn with currcnt us ordinates and thcimpressed voltage on thc anode as abscissa shows the relation lwtwecnthese two quantities. It will hc sccn that whcn the current rcachcs acor tnin value fu rthcr incrcasc in voltage has no etl'cct. Thetclnpcl'uturc of thc cathode. in this case is constant. If thetemperature till should be increased the value of the saturation currentwould also increase. In any case, however, there will be a point atwhich further increase of voltage will produce no increase in thecurrent.

In Fig. 4 I have illustrated the relation between the grid potential andanode potential of a device, such as 4 in Fig. 1. In this case theordinates represent the grid potentials, those below the axis, X-Xrepresenting negative grid potential, and the abscissae represent theanode potential necessary to maintain constant current with varying gridotential. The lower curve Brepresents t e relation between the twopotentials when no current passes through the device, and the uppercurve 0' represents the same relation for one particular value of thecurrent. In the device of which this is a characteristic curve it willbe seen that a variation of one volt in the grid potential correspondsto a variation of practically 150 volts in anode potential, thus it willbe seen that 150 fold amplification may be secured with this particulardevice by the method which I have described. The slope of the constantcurrent curve will depend upon the construction and arrangement of theelectrodes and grid, and I have found it possible to construct devicesof this character by means of which a greater degree of amplificationthan 150 may be secured.

While I have described my method of amplification with special referenceto a system in which a strongly damped antenna is employed it is alsoadapted for use with a tuned antenna as well. It will also be apparentto one skilled in the art that many variations in the arrangement of thedifferent devices employed and in the characteristics of the connectingcircuits may be made without departing from the scope of the appendedclaims, and I do not wish to be limited to the particular arrangementdescribed. Neither do I wish to be limited to the use of apparatus whichoperates with a pure electron discharge, as amplification according tothe method described/may be successfully carried on with any controllingdevice in which the How of current or the potential between twoelectrodes may be varied by varying the potential on a conducting bodyinterposed between or placed in the neighborhood of the electrodes, orwith any current limiting device in which an increase in voltage above acertain point does not produce an increase of current.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. The combination in a wireless receiving system of an electrondischarge device comprising an evacuated envelope having therein anelectron emitting cathode, an

anode and a grid, means for impressing received waves upon the gridcircuit of said device, a source of energy in the plate circuit of saiddevice a current limiting device in series with said source of enerwhich prevents any increase of current in t e plate circuit above acertain amount irrespective of the voltage applied thereto, a secondelectron discharge device similar to the first, and means for impressinupon the grid circuit of the second eectron discharge device thepotential variations between the terminals of said current limitingdevice.

2. The combination in a. wireless reoeiw ing system of a strongly dampedantenna, means for amplying al of the waves of radiant energy receivedby said antenna, means for limiting the amplitude of said amplifiedwaves to a predetermined value which is independent of the voltage ofthe source by which they are produced, means for selecting from saidamplified waves of limited amplitude those of a desired frequency andmeans for detecting the waves thus selected.

3. The combination in a .wireless receiving system of a plurality ofelectron discharge devices each havin an electron emitting cathode, acooperating anode and a conducting grid, means comprising a. nonresonantcircuit for causing variations in the potential of the grid of one ofsaid devices corresponding to received waves means comprising a secondnon-resonant circuit for ampli ying these potential variations andimpresing them on the grid of a second device, thereby producinamplified waves in the plate circuit of t at device, means for limitingthe current in the second non-resonant circuit to a redetermined valueirrespective of the vote therein, a tuned circuit in operative relationto said second device for selecting from the amplified waves those of adesired frequency, and means for detectin the waves thus selected.

4. The combination with an electron discharge device comprising anevacuated envelope having therein an electron emitting cathode, an anodeand a grid, of means for impressing a variable potential upon said grid,a source of energy in the plate cirsuit of said device, a currentlimiting device in series with said source of ener which prevents anyincrease of current 1n the plate circuit above a certain amountirrespective of the voltage ap liedthereto, a second electron dischargeevice similar to the first and means for impressing upon the grid of thesecond device the potential variations between the terminals of saidcurrent limitin device.

5. The combination in a wireless receivmg system of an antenna, meansfor amplitying the waves of radiant energy received by said antenna andmeans for limiting the amplitude of said amplified waves to a.predetermined value which is independent of the voltage by which theyare produced.

6. The combination in a wireless receivin system. of an antenna, meansfor amplifying the waves of radiant energy received b said antenna, andmeans for absorbing all of the energy of said amplified waves above thatcorresponding to a current of a certain predetermined value.

7. The combination in a wireless receiving system of an antenna, meansfor amplifying the waves of radiant energy received bv said antenna,detecting apparatus operatively connected to said antenna and means forabsorbing all of the energy of said amplified waves above thatcorresponding to a current of a predetermined value before they reachthe detecting apparatus.

8. The combination in a wireless signaling system of an antenna, meansfor amplifymg the waves of radiant energy received by said antenna,detecting apparatus operatively connected to said antenna and means forlimitin the. amplitude of the received and am lilied waves to apredetermined value w ich is independent of the volta producing thembefore they reach the (etectin apparatus.

9. The combination in a wireless receiving system of an antenna, meansfor amplifying the potential variations of the waves of radiant energyreceived by said antenna, means for producing a current which varies inaccordance with said amplified potential variations, means for limitingthe amplitude of said current to a predetermined value which isindependent of the voltage by which it is produced, means for selectingfrom said variable current waves of a desired frequency, and means fordetecting the waves thus selected.

10. The combination in a wireless receiving system of an electrondischarge device comprising an evacuated envelope having therein anelectron emitting cathode, an anode and a grid, means for impressingreceived waves upon the grid circuit of said device, a source of energyin the plate circuit of said device, a second electron dis-- char deviceadapted to'limit the current in t e plate circuit of the first device toa predetermined value irres ctive of the voltage applied thereto, athird electron discharge device similar to the first. and means forimpressing upon the grid circuit of the third device the potentialvariations between the terminals of said second device.

11. The combination with an electron discharge device comprising anevacuated envelope having therein an electron emitting cathode, ananode, and a grid, of means for im ressing a variable potential uponsaid gri a source of energy in the plate circuit of said device, asecond electron discharge device adapted to limit the g 14. Means foramplifyingl ing system of an antenna, means for amplifying waves ofradiant energy received by said antenna without any substantialvariation in the wave shape, means for limiting the amplitude of said amlified waves to a predetermined value which is independent of thevoltage by which they are produced, and means for detecting saidamplified waves of limited amplitude.

13. The combination in a wireless receiving system, of means foramplyfying the potential variations of the received waves comprising acontrolling device having at least two electrodes and a controllinggrid, a source of energy connected to sai electrodes and having inseries therewith a device adapted to revent the current between saidelectrodes From exceeding a redetermined value irrespective of the votage imressed thereon from said source, means for impressing thepotential variations of the received waves upon the controllin id, andmeans for impressing the ampli e potential variations upon the grid of asecond controlling device.

potential variations comprising a contro ing device having at least twoelectrodes and a controlling grid, a source of energy connected to saidelectrodes having in series therewith a device adapted to prevent thecurrent between the electrodes from exceeding a redetermined valueirrespective of the vo tage impressed thereon from said source, andmeans for impressing the potential variations to be am lified on thecontrolling grid.

15. 'l he combination with a controlling device having at least twoelectrodes and a controlling grid of a source of energy connected tosaid electrodes and having in series therewith a device adapted toprevent the current between the electrodes from exceeding apredetermined value irrespective of the volta impressed thereon fromsaid source, an means for impressing a variable potential on the centre16. The combination in a wireless receiving system of means foramplifying the potential variations of the received waves comprising acontrolling device having at Ill ling grid. 1'0

least two electrodes and a controlling grid, II

a source of energy connected to said electrodes and having in seriestherewith a device adapted to prevent the current between saidelectrodes from exeeedin a pre determined value irrespective of t evoltage impressed thereon from said source and means for impressing thepotential variations of the received waves on the controllin grid.

. 17. l he method of amplifying potential variations which consists incausing a constant current to flow in a circuit comprisin two separatedelectrodes having interposed between them a controlling grid and at thesame time impressing the otential variations which are to be ampliliedon the controllin rid, thereby producing potential variations betweenthe electrodes similar to the potential variations impressed on the gridbut of much greater amplitude.

18. The combination of arepeating circuit comprising an electrondischarge device having two windings in series therewith, means forinducing an alternating potential from a selected source together withdisturbing potentials in one of said windings. and a second circuithaving a winding therein operatively related to the second winding, saidelectron discharge device being so constructed and the saturationcurrent thereof having such a value that the current flowing in thesecond winding cannot exceed the maximum value of the current derivedfrom the selected source irrespective of the value of the disturbingpotential induced in the first winding.

19. The combination of a repeating circuit comprising an electrondischarge device having two electrodes and two windings in seriestherewith, and means for inducin an alternating potential from aselected source together with disturbing potentials in one of saidwindings. the saturation current of said electron discharge device havinsuch a value that the current flowing in t e sec ond winding cannotexceed the maximum value of the current from the selected sourceirrespective of the value of the disturbing potential induced in thefirst winding.

20. In a repeating system the combination of an electron dischargedevice comprising an evacuated container having two electrodes enclosedtherein provided with means for heating to incandescence, said devicebeing so constructed and the temperature of the electrodes being sochosen that the current passing between said electrodes cannot exceed apredetermined desired value irrespective of the voltage applied thereto.

21. The combination of a repeating circuit comprising an electrondischarge device having two electrodes, at least one of which isprovided with means for heating to incandescence and means forimpressing upon said circuit an alternating potential from a selectedsource together with disturbing potentials, said electron dischargedevice being so const acted and the temperature of the incand scentelectrode being so chosen that the current flowing in the circuit cannotexceed the maximum value of the current derived from the selected sourceirrespective of the value of the disturbin potentials impressed upon thecircuit and will vary between this maximum value and a substantiallyzero value with variations in the amplitude of the alternating potentialfrom the selected source.

22. The method of eliminating disturbing eil'ects in a signaling systemcomprising an electron discharge device having a plurality ofelectrodes, at least one of which iG provided with means for heating tolllcfllhdescence, the temperature of said heated electrode being sochosen that the current passed by said device cannot exceed a givendesired value irrespective of the applied voltage, which consists inproducing in the iystem by means of the maximum energy mm a selectedsource a signaling voltage approximately equal to that required to pro'duce maximum current in the device and applying this voltage togetherwith any voltages which may be produced in the system by means of theenergy of disturbing agencies to said device and thereby producing inthe system currents which will vary only between the maximum value ofthe current produced by the selected source and a substantially zerovalue.

23. The method of transferring electrical energy of a selected sourcefrom one circuit to another by means of an intermediate circuit, whichconsists in limiting the current in the intermediate circuit to a valuesubstantially equal to the maximum value of current which can be derivedfrom the selected source irrespective of the voltage aplied theretowhile maintaining the continuity of the intermediate circuit.

24. In a receiving system for radio communication, a current limitingdevice comprisin an electron discharge device, an electrical circuitconnected to electrodes of said device, a wave responsive deviceassociated with said circuit and means for im pressing upon theelectrodes of said device currents produced by signaling waves togetherwith currents produced by disturbing ncies, the electron producing meansof said device being so adjusted that the current carried by theproduced electrons cannot a preciably exceed in value the current proneed in the circuit by the signaling waves.

25. The combination in a signaling system which is subject to abnormalpotentials of an electron discharge device, an electrical circuitarrangement which includes two windings in series with said device andmeans for inducing a signaling potential from a selected source in oneof said windings, said electron discharge device being so constructedand the saturation current thereof adjusted to such a value that themeans current flowing in the second winding can only vary in valuebetween the maximum value of current derived from the selected sourceand a substantially zero value. irreapective of the value of anyabnormal rst current flowing in the second winding will vary between amaximum and a substantially zero value with variations in the signalingpotential and cannot appreciably exceed in value the maximum value 0 theculirent produced by the signaling potentia 27. The method of operatingan energy transmission system. which is subject to abnormal energyconditions and which comprises a circuit containing a device which rmitsof current flow therethrough in th directions and which is adjusted tolimit the current flowing in that circuit to a predetermined valueirrespective of the to tage applied thereto without interrupting thecontinuity of the circuit. which consists in producing by means of thenormal energy in the system a voltage of substantially the valuerequired to produce the l lh It t the t l ll pying isvoageo c1rcui.o ier:dith any other voltages which may bfi produced in the sy ste'm byabnormal ene and thereby limiting the rate at Mich gnormal energy istransnitted to a value substantially equal to the rate atewhich thenormal energy in the system is transmitted. 28. The method ofeliminating disturb ing efiects in a signaling in comprising an electrondischarge vice ha a plurality of electrodes. at least one of which ISprovided with means for heating to 111- candescence, the temperature ofsaid heatcd electrode being so chosen that the current pamed hvsaiddevice cannot exceed a given desired value i ire of theap plied.energ'. which consists in producing III the system by means of thenormal energy from a selected source a variable signalirg vol themaximum value of which is a proximately equal to that rcquimd to producea current of a value equal to the maximum current which can be ssed bysaid device and applving to the evice this voltafi together with anyvolages which may produced in the sys'trmby means of the energy ofdisturhingagcncles and there current in the circuit,v

by limiting currents produced in the svstem by the disturbing agenciesto a va ue which is substantially equal to that of the maximum currentsproduced by the variable signaling voltage.

29. The combination in a signaling system which is subject to abnormalpotentials of an electron dischar device. an electrical circuit whichinclu es two windings in series with said device, and means for inducinga signaling tential from a selected source in one of said windings, saidelectron discharge device being capable of permitting current to flow inboth directions through said windings and being so constructed and thesaturation current thereof adjusted to such a value that the currentflowing in the second winding cannot appreciably exceed in value thecurrent produced therein by the signaling potential from the selectedsource irrespective of the value of any abnormal potentials which may beinduced in the first winding.

30. In a receiving system for radio communication, a currentlimitidevice comprising an electron discharge evice having a cathode adaptedto be heated to incandescence to serve as a source of electrons and ananode. an electrical circuit connected to the electrodes of said device,a wave responsive device associated with said circuit, and means forimpressing upon the electrodes of said device currents produced bysignaling wavestogcther with currents produced by disturbing agencies,the tem rature of said cathode being so adjusted t at the currentcarried by the electrons emitted thereby cannot appreciably exceed invalue the current produced in e circuit by the signaling WYIVGS.

31. The combination in an ene transmitting system which is subject to anormal energy device havin two electrodes. both of which are rovid withmeans for heating to incan essence, an electrical circuit con betweensaid two elcdotrodes, andolmeans for im resi u sai circuit av tage produed by he ii i rmal energy from a selected source together with voltagesproduced by abnormal. energy conditions. said electron discharge devicebei so constructed and the tem rature of incandescent, electrodehemgsochosen that the current in the "circuit cannot appreciably exceed invalue thecurrent produced therein by the voltage roduced by the normalenergy from the se- Footed source.

' 32. The method of eliminating disturbing ofiectsin a s'system'co'mprising an electron discharge device having a plurality ofelectrodes. at least. one of which is pro- 'vided with means for heatingto incandescanoea the temperature of said heated electrodbeingsoehosenfl hecumu passed conditions of an electron discharge bysaid device cannot exceed a 'ven desired value irrespective of the appied voltage, which consists in producing in the system y means of thenormal energy from a selected source a signaling voltage approximatelyequal to that required to produce maximum current in the device, andapplying this voltage together with any voltages which may be producedin the system by means of the encrg of disturbing agencies to saiddevice and hereby limiting currents produced in the system by thedsturbing agencies to a value which is substantially equal to that ofthe currents produced by the signaling voltage. a

33. The combination in a signaling system which is subject to abnormalpotentials of an electron discharge device. an electrical circuitarrangement which includes two windings in series with said device. andmeans for inducing a signaling potential from a selected source in oneof said windings. said electron discharge device being so constructedand the saturation currentthereof adjusted to such a value that thecurrent flowing in the second winding cannot appreciably exceed in valuethe current produced therein by the signaling potential from theselected source irrespective of the value of any abnormal potentialswhich may be induced in the first winding.

34. The method of operating an energy transmission system, which issub'ect to abnormal energy conditions and w ich comprises a circuitarrangement containing a device which is adjusted to limit the currentflowing in that circuit arrangement to a predetermined value irres tiveof the voltage applied thereto wit out interrupting the continuity ofthe circuit arrangement which consists in producing by means 0%thenormal energy in the system a voltage of substantially the valuerequired to produce the maximum possible currents in the circuitarrangement, applying this voltage to the circuit arrangement, togetherwith any other voltages which may be produced in the system by abnormalener and thereby limiting the rate at which a normal energy istransmitted to a value substantially equal to the rate at which thenormal energy in the system is transmitted.

35. The combination in an energy transmitting system which is subject toabnormal energy conditions, of an electron discharge device having aplurality of electrodes, at least one of which is provided with meansfor heating to incandescence, an electrical circuit arrangementconnected with said electrodes, and means for impressing upon saidcircuit arrangement a voltage produced by the normal energy from theselected source together with voltages produced by abnormal energyconditions, said electron discharge device being so constructed and thetem rature of the incandescent electrode being so chosen that thecurrent in the circuit arrangement cannot ap reciably excecd in valuethe current pro uced therein by the voltage produced by the normalenergy from the selected source. n witness whereof, I have hereunto setmy hand this 9th day of December, 1914.

IRVING LANGMUIR.

Witnesses:

WILLIAM C. WHITE, BENJAMIN B. HULL.

Certificate of Correction. It is hereby certified that in Imtters PatentNo. 1,468,116, granted upon the application of Irving Lan nuir. ofSchenectady, New York, for an impmvement in Methods of and leans forAmplifying Potential Variations, an error appears in the printedspecification requirm correction as follows: Page 1, line 30, strike outthe words provide a simple an efficient means for and insert instead theliable and words -troden, one of which is provided with mean; and thatthe saifl Letters Patent should-be read with this correction thereinthat the same ma conform to the reoord of the (use in the Patent Oflice.

Sigma and sealed this 23d day of October, A; D., 1923.

[SEAL-.1 W A; KINNAN,

' Acting Gommisaioner of Pdtnta.

